The present invention relates to automatic transmissions for land vehicles and, more particularly, to a universal torque converter clutch system including a hybrid lock-up piston/damper plate subassembly, which is designed for installation in the torque converters of automatic transmissions from various manufacturers, namely, BORG WARNER, ALLISON, FORD, GENERAL MOTORS, and CHRYSLER or other similar automatic transmissions.
For purposes of this application the term “hybrid” will be understood to define the present lock-up piston/damper plate subassembly having components with features and characteristics derived from both the original equipment manufacture lock-up piston and damper plate components as provided with BORG WARNER, ALLISON, FORD, GENERAL MOTORS, and CHRYSLER transmissions (hereinafter “the subject transmissions”).
The torque converter of an automatic transmission replaces the clutch used in manual transmissions. It is the primary component for transmittal of power between the engine and the transmission in an automotive vehicle. The basic principle of torque converter operation can be observed by placing the blades of two electric fans opposite each other and turning on one of the fans. If one of the fans is turned on, the force of the air column produced will act upon the motionless blades of the other fan, which will begin turning and eventually reach a speed approaching the speed of the powered fan. The torque converter employs an analogous mechanism using automatic transmission fluid (hereinafter “ATF”) to provide a fluid coupling between the engine and the transmission of an automobile, which provides for a smooth conversion of torque from the engine to the mechanical components of the transmission.
During the torque converter lock-up cycle, the torque converter clutch 120 (see FIG. 1) is applied to eliminate the slippage that occurs through the fluid coupling and to provide a direct mechanical drive for efficient transfer of engine torque to the drive wheels. More particularly, during the lock-up cycle the torque converter clutch 120 is shifted axially forward by ATF pressure and frictionally engages an inner surface of the torque converter cover 125 to affect such direct mechanical drive. The torque converter cover 125 rotating at engine speed instantaneously engages the damper plate assembly 146 (see FIG. 3) when actuated by the lock-up piston 142, which serves to transmit the rotational torque of the engine directly to the transmission. The damper plate assembly 146 functions to absorb the sudden impact of such direct mechanical drive engagement to prevent damage to the turbine shaft and also to the friction materials within the torque converter clutch 120.
Still referring to FIG. 3 the prior art damper plate assembly 146 includes an array of radially disposed damper springs 147 having a predetermined strength (i.e. spring rate), which are permanently captured in the riveted construction of the prior art damper plate assembly. The strength of such damper springs 147 is factored into the design of the damper plate assembly 146 based on the factory specified peak engine torque generated in a given vehicle engine, which is critical to the proper function of the lock-up clutch.
However, in the automotive aftermarket various engine-tuning modules are marketed for truck engines utilizing the subject transmissions, which deliver the most powerful, street-legal tuning available for towing the maximum loads allowed by the vehicle manufacturer. At such higher horsepower gains the original equipment manufacture (hereinafter “OEM”) lock-up clutch 120 including the damper plate assembly 146 is often overmatched and prone to failure.
More particularly, it is well known in the industry that when the subject transmissions, which were initially designed to operate behind a truck engine manufactured to a factory torque specification, are utilized in a higher horsepower application, the spring strength of the OEM damper plate assembly 146 is inadequate and the damper springs 147 may be compressed beyond their working limits. This results in mechanical damage to the damper plate assembly 146, friction rings 130, and also to the turbine shaft spline as at 153 (FIG. 1) during the torque converter lock-up cycle and other peak torque events.
Thus, the present invention has been developed to resolve this problem and other shortcomings of the prior art.